Search for new physics in light of interparticle potentials and a very heavy dark matter candidate

Abstract

It is generally well known that the Standard Model of particle physics is not the ultimate theory of fundamental interactions as it has inumerous unsolved problems, so it must be extended. Deciphering the nature of dark matter remains one of the great challenges of contemporary physics. Supersymmetry is probably the most attractive extension of the SM. In the first part of this thesis we study the interparticle potentials generated by the interactions between spin-1/2 sources that are mediated by spin-1 particles in the limit of low momentum transfer. We investigate different representations of spin-1 particle to see how it modifies the profiles of the interparticle potentials and we also include in our analysis all types of couplings between fermionic currents and the mediator boson. The spin- and velocity-dependent interparticle potentials that we obtain can be used to explain effects possibly associated to new macroscopic forces such as modifications of the inverse-square law and possible spin-gravity coupling effects. The second part of this thesis is based on the dark matter phenomenology of well-motivated $U(1)'$ extensions of the Minimal Supersymmetric Standard Model. In these models the right-handed sneutrino is a good DM candidate whose dark matter properties are in agreement with the present relic density and current experimental limits on the DM-nucleon scattering cross section. In order to see how heavy can the RH sneutrino be as a viable thermal dark matter candidate we explore its DM properties in the parameter region that minimize its relic density via resonance effects and thus allows it to be a heavier DM particle. We found that the RH sneutrino can behave as a good DM particle within minimal cosmology even with masses of the order of tens of TeV, which is much above the masses that viable thermal DM candidates usually have in most of dark matter particle models.